Package org.locationtech.jts.operation.valid

Class IsSimpleOp

  • public class IsSimpleOp
extends Object
    Tests whether a Geometry is simple as defined by the OGC SFS specification.

    Simplicity is defined for each Geometry type as follows:

    • Point geometries are simple.
    • MultiPoint geometries are simple if every point is unique
    • LineString geometries are simple if they do not self-intersect at interior points (i.e. points other than the endpoints). Closed linestrings which intersect only at their endpoints are simple (i.e. valid LinearRingss.
    • MultiLineString geometries are simple if their elements are simple and they intersect only at points which are boundary points of both elements. (The notion of boundary points can be user-specified - see below).
    • Polygonal geometries have no definition of simplicity. The isSimple code checks if all polygon rings are simple. (Note: this means that isSimple cannot be used to test for all self-intersections in Polygons. In order to check if a Polygonal geometry has self-intersections, use Geometry.isValid()).
    • GeometryCollection geometries are simple if all their elements are simple.
    • Empty geometries are simple
    For Lineal geometries the evaluation of simplicity can be customized by supplying a BoundaryNodeRule to define how boundary points are determined. The default is the SFS-standard BoundaryNodeRule.MOD2_BOUNDARY_RULE.

    Note that under the Mod-2 rule, closed LineStrings (rings) have no boundary. This means that an intersection at the endpoints of two closed LineStrings makes the geometry non-simple. If it is required to test whether a set of LineStrings touch only at their endpoints, use BoundaryNodeRule.ENDPOINT_BOUNDARY_RULE. For example, this can be used to validate that a collection of lines form a topologically valid linear network.

    By default this class finds a single non-simple location. To find all non-simple locations, set setFindAllLocations(boolean) before calling isSimple(), and retrieve the locations via getNonSimpleLocations(). This can be used to find all intersection points in a linear network.

    Version:
    1.7
    See Also:
    BoundaryNodeRule, Geometry.isValid()

    • Constructor Detail

      • IsSimpleOp

        public IsSimpleOp​(Geometry geom)
        Creates a simplicity checker using the default SFS Mod-2 Boundary Node Rule
        Parameters:
        geom - the geometry to test

      • IsSimpleOp

        public IsSimpleOp​(Geometry geom,
                  BoundaryNodeRule boundaryNodeRule)
        Creates a simplicity checker using a given BoundaryNodeRule
        Parameters:
        geom - the geometry to test
        boundaryNodeRule - the boundary node rule to use.

    • Method Detail

      • isSimple

        public static boolean isSimple​(Geometry geom)
        Tests whether a geometry is simple.
        Parameters:
        geom - the geometry to test
        Returns:
        true if the geometry is simple

      • getNonSimpleLocation

        public static Coordinate getNonSimpleLocation​(Geometry geom)
        Gets a non-simple location in a geometry, if any.
        Parameters:
        geom - the input geometry
        Returns:
        a non-simple location, or null if the geometry is simple

      • setFindAllLocations

        public void setFindAllLocations​(boolean isFindAll)
        Sets whether all non-simple intersection points will be found.
        Parameters:
        isFindAll - whether to find all non-simple points

      • isSimple

        public boolean isSimple()
        Tests whether the geometry is simple.
        Returns:
        true if the geometry is simple

      • getNonSimpleLocation

        public Coordinate getNonSimpleLocation()
        Gets the coordinate for an location where the geometry fails to be simple. (i.e. where it has a non-boundary self-intersection).
        Returns:
        a coordinate for the location of the non-boundary self-intersection or null if the geometry is simple

      • getNonSimpleLocations

        public List<Coordinate> getNonSimpleLocations()
        Gets all non-simple intersection locations.
        Returns:
        a list of the coordinates of non-simple locations